This invention relates to coiling machines, particularly for pattern or program coiling of resistance wire into coils with periodic close winding and space winding portions.
Coils of resistance wire, used largely for heating elements, instrumentation and the like, are formed from wire on helical coiling machines such as those disclosed in U.S. Pat. Nos. 4,258,561 and 4,208,896 and application Ser. No. 652,509 filed Sept. 20, 1984. Sometimes it is desirable to have such coils possess portions of closely wound turns and intermittent portions of spaced turns. Heretofore, the only practical technique believed to be used to produce coils having both such close and space winding, i.e. known as pattern coiling or program coiling, has been to insert a thin blade into the spinning coil between the turns to spread the wire turns where spacing is needed. The spacing achieved by this technique is limited to a dimension which is approximately equal to one wire thickness at a maximum. Attempting greater spacing results in the spinning coil buckling and destroying itself. Thus, any greater spacing must be laboriously achieved using manual jigs and fixtures.
It should be understood that coiling, including space coiling, of spring wire is basically different than coiling of resistance wire. Spring wire can be pushed against a fixed curve tungsten carbide forming block to coil it. Thus, by simply moving the block in relation to the incoming end or point of wire, practically any pattern of spring coiling can be readily produced. But, resistance wire must be pulled to coil it, not pushed. Thus, resistance wire coiling machines use a rotating coiling arbor and adjacent coiling rolls cooperative therewith. The temper of resistance wire is only a fraction of that of spring wire. Being typically an alloy of high chrome and nickel content, the wire is subject to molecular marriage, i.e. "cladding", which takes place if the wire is pushed against any fixed surface with pressure sufficient to form a coil, thereby destroying the constant resistance of the wire and hence the usefulness of the coil itself. Therefore, space coiling of resistance wire has been somewhat difficult to achieve and definitely limited in results.
It would be advantageous to be able to space coil right on a coiling machine as the coil is being formed, to a spacing significantly greater, even many times greater, than the diameter of the wire strand, and/or to readily vary the spacing of a coil as it is formed, and/or to pattern or program coil to controlled intermittent close and space coiling as the coil is formed on the arbor of the coiling machine.